Insight into boron-doped biochar as efficient metal-free catalyst for peroxymonosulfate activation: Important role of-O-B-O- moieties

In recent years, metal-free catalysts for persulfate-mediated oxidation processes have been widely applied to remove contaminants in the aquatic environment. Herein, a simple pyrolysis approach was used to synthesize the boron doped biochars (B@TBCs) derived from boric acid mixed with tea seed shells powders. The obtained B@TBCs exhibited fantastic capability to boost PMS (0.5 mM) activation for 90%~ removal of oxytetracycline (OTC) within 20 min. Through the correlation analysis and DFT calculations, it was concluded that the apparent rate constant of pollutants removal was greatly related to the-O-B -O-groups on the biochars, which could improve the electron-donating capacity of the biochar. In addition, the degradation process of OTC was pH -dependent because of the changed roles of ROSs under different pH. Finally, according to the DFT calcula-tion, LC-MS and toxicological analysis, the degradation pathways of pollutants and the toxicity changes during the degradation process were obtained. These findings consolidated the theoretical basis for further boosting the catalytic activity of B-doped biochars and expanded the imagination for the modification of other metal-free biochar catalysts for PMS activation.

Automated summary

In recent years, metal-free catalysts have been widely used to remove contaminants in water. This study synthesized boron-doped biochars through a simple pyrolysis approach and found that they exhibited excellent capability to activate persulfate for efficient oxytetracycline degradation. The study also investigated the influence of the-O-B-O-groups on the biochars on the degradation rate and found that they enhanced the electron-donating capacity of the biochars. Additionally, the degradation process of oxytetracycline was pH-dependent and the degradation pathways and toxicity changes during the process were determined.